Thermally controlled electrical switch having motion-amplifying lever means



A. MORO TROLLED ELEG N-AMPLIFYING Dec. 14, 1965 THERMALLY CON TRICALSWITCH HAVING MOTIO LEVER MEANS Filed Sept. 9, 1964 MF L "mum M Inventor)4/vr0/v/0 Moleo A ttorriey United States Patent 3,223,806 THERMALLYCONTROLLED ELECTRICAL SWITCH HAVING MOTION-AMPLIFYING LEVER MEANSAntonio Moro, Piazza Po 6, Milan, Italy Filed Sept. 9, 1964, Ser. No.395,260 Claims priority, application Italy, Sept. 10, 1963, 18,556/ 63 4Claims. (Cl. 200138) This invention relates to thermally controlledelectrical switches and is an improvement in or modification of theinvention disclosed in the specification of co-pending patentapplication Serial No. 279,104.

The said specification describes a thermally controlled electricalswitch with a metallic housing for automatically closing and opening anelectrical circuit in accordance with predetermined limits oftemperature of the medium surrounding the thermal element of the switch,the said limits being adjustable from the exterior of the housing.

One object of the present invention is to render the adjustment of theswitch more accurate and reliable.

In accordance with the present invention there is provided a thermallycontrolled electrical switch having a metallic housing, the switch beingof the type in which a movable contact is subjected to the opposingactions of resilient means and of a bimetallic member in the form of acurved disc disposed on the base of the housing and adapted to reverseits curvature at predetermined limits of temperature of the said medium,and in which a movable contact is carried by an arm, disposed along theaxis of the housing, of a bent lever the other arm of which extendsparallel to the disc and is connected at one end to a fixed point,within the said housing, about which it can turn under the action of thedisc and the said resilient means, whereby there is imparted to themovable contact a displacement greater than the movement of the disc soas to move it into and out of engagement with the fixed contact to closeand open a circuit in which the switch is included, the fixed contactbeing carried, within the housing and facing the movable contact, by thefree end of a supporting strip the other end of which is fixed to ametallic sector located between the insulating cover of the housing andan insulating ring bearing on a shoulder of th housing, and iselectrically connected to a terminal carried by the cover.

An embodiment of the by way of example with drawing, in which:

FIG. 1 is an axial section of a switch according to the invention, takenon the plane of movement of the movable contact of the switch, and

FIG. 2 is a transverse section of IIII of FIG. 1.

The switch illustrated comprises a cylindrical metallic housing C in thebase of which is located a bimetallic plate B of disc form associatedwith a flat spring M and a right angle lever L carrying the movablecontact, and a cap or cover 1 of plastic insulating material carryingterminals 2 and closing the open end of the housing C, the cover 1 beingclamped against an annular shoulder 7 within the housing with interposedrings of insulating material, by upsetting the upper rim of the housing.

invention will now be described reference to the accompanying the switchon the line The terminals 2, 2" of the switch are of the fiat plug type,arranged at the centres of recesses 2 formed in the cap and adapted toreceive socket sleeves. Such terminals are practicable and easy to use,and the walls of the recesses ensure complete electrical insulation,against the exterior.

On the lower ends 3, 3" of the terminals 2', 2" springs 4', 4" arethreaded in electrical contact with those lower ends. The spring 4'establishes metallic continuity and hence electrical continuity betweenthe terminal 2' and a movable contact 5 via a sector 6 and a flexiblemetallic strip 7 clamped between the sector 6 and the insulating ring7'.

The spring 4" establishes metallic and hence electrical continuitybetween the terminal 2" and a normally fixed adjustable contact 8 via asector 9 and a support in the form of a bent flexible strip 10 on whichthe contact 8 is fixed.

The movable contact 5 is fixed to the free end of the long arm,extending parallel to the axis of the housing C, of the lever L, thesaid long arm being straight. The normally fixed adjustable contact 8carried by the end of the flexible strip 10 is disposed exactly facingthe movable contact 5. It is fixed on the strip 10 together with alaterally extending projection 13 and an insulating plate 14 whichcovers the projection 13 on the side thereof nearest the wall of thehousing C.

Parallel to a screw V provided for adjustment of the spring M (asdescribed in the above-mentioned specification) there is provided foradjustment of the contact 8 a screw 11 which is screwed into the housingC and the inner end 12 of which bears against the insulating plate 14and thus acts through it on the projection 13 to adjust the position ofthe contact 8 according to the extent to which the screw 11 is screwedinto the housing C, the position of the contact 8 being maintained bythe resilience of the strip 10.

A switch according to the invention as above described presentsimportant advantages: in fact, it enables the cover or cap 1 to be madecompletely independent of the movable contact 5, and any deformationthereof has no effect on the position of the contact itself, which mayfurther be put into the operating position before the cap is applied andconsequently may be inspected before the switch is closed. The form ofthe terminals is also advantageous, permitting more rapid and certainconnection of the cables of the electrical circuit.

What I claim is:

1. In a thermally controlled electrical switch having a metallic housingand a cover of insulating material, a movable contact, a bimetallicplate disposed in the base of the housing and adapted to reverse itscurvature at predetermined limits of temperature of the mediumsurrounding the plate, an arm carying the movable contact, means fortransmitting motions of the bimetallic plate to the arm thereby tomultiply the motion of the bimetallic plate, and a fixed contact; theimprovement comprising terminals carried by the cover, flexibleconductors leading to the contacts, and spiral spring means inelectrical contact at one end with the terminals and at the other endwith said flexible conductors.

2. Structure as claimed in claim 1, and a screw adjustable in thehousing by screwing it from the exterior thereof, said flexibleconductorleading to said fixed contact being bent in such a manner thatits end bears resiliently on the end of said screw thereby to permitpositioning of the fixed contact relative to the movable contact.

3. Structure as claimed in claim 2, and a second screw side by side withsaid first-named screw and acting against said movable contact to adjustthe rest position of said movable contact.

4. Structure as claimed in claim 1, in which said terminals are in theform of flat plugs, and peripheral insulating and protecting wallsformed integrally with the cover and surrounding said plugs.

References Cited by the Examiner UNITED STATES PATENTS 1,522,786 1/ 1925MacNeil 200-113 2,722,666 11/ 1955 Hodgkins 339-256 2,750,475 6/1956Clason 200-139 2,751,464 6/1956 Short et al. 200-139 3,015,687 1/1962Ruscito 339-198 FOREIGN PATENTS 596,423 7/1959 Italy.

ROBERT K. SCI-IAEFER, Acting Primary Examiner. BERNARD A. GILHEANY,Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,223,806 December 14, 1965 Antonio Moro It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

In the grant, line 3, after "Italy," insert assignor to Soc. per AzioniFratelli Borletti, of Milan, Italy, a company of Italy, line 12 for"Antonio Moro, his heirs" read Soc. per Azioni Fratelli Borletti, itssuccessors in the heading to the printed specification, line 5, for"Antonio Moro, Piazza Po 6, Milan, Italy" read Antonio Moro, Milan,Italy, assignor to Soc. per Azioni Fratelli Borletti, Milan Italy, acompany of Italy Signed and sealed this 31st day of January 1967.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AttestingOfficer

1. IN A THERMALLY CONTROLLED ELECTRICAL SWITCH HAVING A METALLIC HOUSINGAND A COVER OF INSULATING MATERIAL, A MOVABLE CONTACT, A BIMETALLICPLATE DISPOSED IN THE BASE OF THE HOUSING AND ADAPTED TO REVERSE ITSCURVATURE AT PREDETERMINED LIMITS OF TEMPERATURE OFF THE MEDIUMSURROUNDING THE PLATE, AN ARM CARRYING THE MOVABLE CONTACT, MEANS FORTRANSMITTING MOTIONS OF THE BIMETALLIC PLATE TO THE ARM THEREBY TOMULTIPLY THE MOTION OF THE BIMETALLIC PLATE, AND A FIXED CONTACT; THEIMPROVEMENT COMPRISING TERMINALS CARRIED BY THE COVER, FLEXIBLECONDUCTORS LEADING TO THE CONTACTS, AND SPIRAL SPRING MEANS INELECTRICAL CONTACT AT ONE END WITH THE TERMINALS AND AT THE OTHER ENDWITH SAID FLEXIBLE CONDUCTORS.